patch proposal

[cage]

Hi Peter!

I have a patch for ltk that supposed to do the following:

- remove use of a deprecated function for sbcl:

  "sb-debug:backtrace"

  https://github.com/herth/ltk/blob/master/ltk/ltk.lisp#L5088

  with "sb-debug:print-backtrace"

- prevent ltk to "leak" error messages from other applications (I have
  had problems  with font-config, for example)  into the communication
  pipe with  user application, this  pollute the messages sent  on the
  pipe and makes the application crash.

  I have just added ":error nil" to this line

  https://github.com/herth/ltk/blob/master/ltk/ltk.lisp#L464

  i feel this solution is sub-optimal as is not portable, probably UIOP
  could help here.

- clean a bit the code (mostly comes from Emacs for free ;-) )

Please can you tel me how can I send the patch to be reviewed? Is here
a good place or should I set up a pull request on github?

Bye!
C.